The present invention related generally to electrical standoffs and more particularly to electrical standoffs having a transmission structure formed thereon for coupling extremely high frequency electrical signals.
Transmission structure electrical standoffs are used as transition devices between semiconductor devices having transmission structures. A semiconductor dies, for example, may have coplanar transmission structures formed on one of the horizontal surfaces of the dies. The transmission structure electrical standoff has a coplanar transmission structure that dimensionally and electrically matches the coplanar transmission structure on the semiconductor die. The transmission structure electrical standoff is butted against the semiconductor die with the ends of the coplanar transmission structures of the electrical standoff and the semiconductor die aligned and coplanar. The coplanar transmission structures on the electrical standoff and the semiconductor die are electrically coupled using electrical conductors, such as conductive wires or gold foil. Excessive probing or wire or wedge bonding to the transmission structure on the semiconductor die will remove portions of the gold layer destroying the electrical connectivity of the transmission structure. The transmission structure electrical standoff allows probing of the output of the semiconductor die without contacting the coplanar transmission structure on the die.
The traditional method of manufacturing transmission structure electrical standoffs is to lay down multiple gold transmission structures using a thin or thick film process on a wafer of dielectric material, aluminum oxide or the like. The wafer of dielectric material is then laser scribed and the individual electrical standoffs are snapped off from the wafer. The resulting electrical standoffs has vertically jagged end walls due to the snapping off process. Further, the laser scribing is performed away from the coplanar transmission structure due to the heat generated in the scribing process that would lift the gold layers of the coplanar transmission structure away from the substrate.
The resulting electrical standoff has drawbacks when used in extremely high frequency electrical signal applications. The combination of the jagged vertical end walls and the placement of the ends of the coplanar transmission structure away from the vertical end walls requires longer electrical connectors between the coplanar transmission structures. The longer electrical connectors and the air gap between the electrical standoff and the semiconductor die due to the jagged vertical end wall contribute to limit the bandwidth of the coplanar transmission line connection between the electrical standoff and the semiconductor die.
What is needed is a electrical standoff that overcomes the bandwidth limitations of the currently use electrical standoffs. The electrical standoff needs to have vertical end walls that can be butted flush with a semiconductor die. The electrical standoff should also have a transmission structure that extends to the vertical end walls of the standoff. Further, a manufacturing process is needed that produces an electrical standoff that has at least two perpendicular end walls with a coplanar transmission structure that extends to the perpendicular end walls.
Accordingly, the present invention is to an electrical standoff usable for coupling extremely high frequency electrical signals over a transmission structure. The electrical standoff has a dielectric substrate with opposing horizontal surfaces and at least two opposing vertical end walls. A transmission structure having planar elements is formed on the at least one of the horizontal surfaces with the planar elements of the transmission structure extending to the two opposing vertical end walls. In the preferred embodiment, the transmission structure is a coplanar transmission structure formed on one of the horizontal surfaces of the dielectric substrate.
The electrical standoff is manufactured by forming at least a first transmission structure having planar elements on a wafer of dielectric material. A low temperature water soluble wax is applied over the transmission structure on the wafer of dielectric material and a protective covering is applied over the water soluble wax. A coolant is directed onto the wafer of dielectric material and the wafer of dielectric material is sawn to form the electrical standoff. Two of the opposing sawn vertical end walls intersect the planar elements of the transmission structure. The protective covering and low temperature water soluble wax are removed from the electrical standoff.
In the preferred embodiment, a plurality of transmission structures are formed on the wafer of dielectric material. The transmission structures formed on the wafer of dielectric material may be a coplanar transmission structure, a stripline transmission structure, or similar transmission structures. The protective covering may be an adhesive tape. The coolant may take the form of a water jet, refrigerated air or the like that is directed onto the wafer of dielectric material. After the wafer is sawn to form the electrical standoffs, the adhesive tape and the water soluble wax is removed from the electrical standoff.
The objects, advantages and novel features of the present invention are apparent from the following detailed description when read in conjunction with appended claims and attached drawings.